Days before U.S. Border Patrol agents Raul and Fidel Villarreal abruptly quit their San Diego posts in June 2006, the brothers scrambled to get their finances in order.

Fidel, the older brother, withdrew $10,000 from a bank account. Raul claimed to his insurance carrier that his 2000 Mercedes-Benz ML430 had been stolen. Then, under a cloud of suspicion that they had helped smuggle immigrants into the United States while on duty, they left their employer and adopted country for their native Mexico.

A month or so after they resigned, attorneys for the men delivered a message to a federal prosecutor in the U.S. attorney's office in San Diego: The brothers were willing to surrender if they were wanted as a result of a criminal complaint or indictment.

A year later, the attorneys again informed a federal prosecutor that the brothers were willing to turn themselves in, if requested. There was no response, and the request for surrender never came. Fifteen months went by before the brothers were caught in Tijuana, Mexico, just south of San Diego.

Between their attorneys' overture and their capture, the brothers regularly traveled back and forth to visit family in the United States, tried to start a produce business in Tijuana and threatened one of their cohorts with a gun pointed at his head, prosecutors claim.

These are just some of the new details that have come to light through recently filed court documents, six years after the corruption investigation became public.

The brothers' resignation, subsequent flight from the United States and eventual capture made national news. Investigators suspected Fidel and Raul Villarreal, now 43 and 42, respectively, had been tipped off that they were suspected of human smuggling, bribery and other charges, which was a source of friction between agencies responsible for policing corruption. They have pleaded not guilty.

Prosecutors contend that the brothers pocketed more than $1 million in bribes by smuggling immigrants from Brazil and Mexico into the country by using their Border Patrol vehicles in 2005 and 2006 while working with a smuggling organization that included a Tijuana police district chief. They did this as investigators watched from the air and furtively attached tracking devices on government-issued Border Patrol vehicles used sometimes by the brothers. One of the brothers even found such a tracking device, prosecutors claim.

Years later, the brothers continue to fight their prosecution. Their attorneys -- they've gone through several since their extradition -- argue that the government's prosecution is "paper-thin" with circumstantial evidence. A jury trial is scheduled to begin June 19.

Defense attorneys say many of the smuggled immigrants couldn't initially identify the brothers and have challenged the credibility of a key witness who is cooperating with law enforcement. In a court filing earlier this year, attorneys for Raul Villarreal wrote that despite GPS tracking, mounted cameras and aerial surveillance, the government still didn't have conclusive evidence to catch their client. They question why the brothers would go to the trouble of emptying their bank accounts and transferring home-ownership interest to a relative if they had pocketed so much money.

"On the one hand their case alleges millions of dollars in bribes but on the other hand they seek to introduce the withdrawal of defendant's savings totaling only $44,000 and deeding his home to his sister as 'asset protection,' " J. David Nick, Raul Villarreal's attorney, wrote in an April court brief.

The Villarreal brothers are just two of a handful of Customs and Border Protection employees in Southern California charged with corruption-related crimes in recent years to contest prosecution rather than accept a plea agreement.

Oscar Ortiz-Martinez, who worked as a customs inspector in Calexico, and Lorne "Hammer" Jones, an officer at the San Ysidro and Otay Mesa border crossings, were arrested in September 2010 in separate investigations. Both face bribery and drug smuggling charges and are scheduled to go to trial in August.

It wouldn't be a first if any of them are not convicted. Of the 139 Customs and Border Protection employees who have been indicted or convicted of corruption-related charges since October 2004, nearly a dozen have been acquitted or had their charges dropped or dismissed, according to a 2011 internal report obtained by the Center for Investigative Reporting through a Freedom of Information Act request.

For the Villarreal brothers, the courts have not been lenient to date. Earlier this month U.S. District Judge John A. Houston denied the Villarreal brothers' appeal for bond and pretrial release. Magistrate Judge Bernard G. Skomal in February denied an earlier request for release because the brothers were accused of threatening a witness in the case. Skomal indicated that the men faced a conservative sentence of 30 years in prison.

"When they found out they were being investigated, they both resigned, which could be considered an act of admission in and of itself," Skomal said at the February hearing, according to a court transcript. "Instead of fighting and staying on their job, they resigned, transferred their property and moved to Mexico."

Face of the Border Patrol

For years, Raul Villarreal had been the face of the Border Patrol in San Diego, appearing as a spokesman for the agency. He had acted as a callous human smuggler in a public service announcement for the Mexican government that warned would-be immigrants of unscrupulous coyotes, or smugglers.

"It is highly ironic that Raul Villarreal acted as a notorious alien smuggler in the public service announcement video when, in real life, he was an alien smuggler while on duty as a Border Patrol Agent," prosecutors wrote in a court filing this month, asking that the video be entered as evidence. The judge denied the request.

Originally from Jalisco, Mexico, the Villarreal family immigrated to the United States in 1984, arriving in National City, south of San Diego. Neither of the brothers knew English when they came to the United States. Raul was hired first by the Border Patrol in 1995, followed three years later by Fidel.

In late May 2005, Raul Villarreal was suspended for four days without pay following a drunken encounter with police officers from Chula Vista, a city near the U.S.-Mexico border, according to court records.

Raul Villarreal was angry about his suspension, prosecutors claim. He allegedly told his smuggling partners that if they were going to get his boots dirty by being removed from his duties as a public information officer and assigned to patrol again, he was going to make some money.

Four days later, he transported a load of smuggled immigrants on behalf of the smuggling organization, prosecutors contend.

Federal agents from U.S. Immigration and Customs Enforcement, an agency of the Homeland Security Department, and the department's inspector general learned of the brothers' alleged smuggling activities and launched an investigation in May 2005. They subpoenaed phone and financial records, installed pole cameras where the immigrants were dropped off and placed tracking devices on the Border Patrol vehicles that the brothers sometimes used, records show.

The tracking devices showed that the brothers drove the vehicles out of their patrol areas and sometimes outside the designated area of responsibility for their respective Border Patrol stations. In turn, they met up with a footguide and seven to 10 people who had been smuggled across the border and drove them farther into the country, where other drivers would then transport them beyond the border region, court records show. After their shifts ended, the brothers traveled to Tijuana to pick up their bribes, according to court records.

After being tipped off that they were under investigation, the brothers headed to Guadalajara, in their native Mexican state of Jalisco. Prosecutors claim they stayed there for several months and "partied and discussed how they could get away with their crimes" with their partners in crime, including a smuggler named Hector Cabrera. The Tijuana police chief involved with the smuggling organization, Gerardo Santiago Prado, was sprayed with bullets and killed in November 2006, months after the brothers fled to Mexico.

About a year later, in 2007, the brothers learned that agents had arrested drivers recruited by Cabrera to transport illegal immigrants, and the drivers had cooperated with investigators, court records show. Raul Villarreal pointed a gun at Cabrera's head and ordered him to keep his drivers quiet, prosecutors contend.

The brothers were indicted in April 2008 and captured in Tijuana nearly six months later. In March 2009, the Villarreals were extradited to the United States and arrested by federal agents. Since then, they have been detained in San Diego.

Their attorneys say they lived openly in Mexico under their true names, did not try to hide their whereabouts and even hired attorneys to keep them apprised of the investigation. They claim that the brothers were not given an opportunity to surrender and had waived extradition but were kept in Mexico for six months, what Zenia Gilg, an attorney for Fidel Villarreal, likened to "torture" in a Mexico City prison.

"You'll be shocked at what happened in Mexico," she said of upcoming trial testimony. "I don't think there will be much denying."